I can work from home sometimes and I can tell you.. a good hour of my work day normally ends up with me going zzzzzzzzzz. Luckily no-one notices hahah. No idea how people cope with pregnancy when they've already got kids! This is my first and I can't even cope with myself!
I'm going to draw on my experience with my second pregnancy. My first was exhausting, I felt every minute of it. I had trouble moving around when I got to the end (getting off the couch, etc).
With my second, I didn't notice being as tired (probably because I'd already adjusted to being tired all the time!). And I was still squatting down to help my 2 year old on the potty when I was late in to my 3rd trimester with ease, despite weighing about the same as towards the end of my first pregnancy and being further along (when I had to have help getting off the couch! Ha!).
It's like you have less time to be tired, or maybe your body is all BTDT. It's not that it is easier, per se, but you can cope better?
That is what I keep telling myself anyway!